Morphic - The Squeak User Interface
by Juan Manuel Vuletich
User Scripting
Also called
Scripting with Players, this style is a descendent of the Self programming
style. Morphs (i.e. instances of classes from the Morph hierarchy) are visually
assembled. Smalltalk does not allow adding methods to instances, so other
objects (called "Players") are added to hold the scripts.
"In the
User-Scripting style, you construct surface graphics by directly assembling
standard Morphic parts -- e.g. Rectangles, Images, Joysticks, etc., by dragging
them from a Parts Bin and arranging them as desired, and then you add
user-defined state and behavior by adding instance variables and writing
methods for "Players" who represent the individual morphs you wish to
script.
The user thus
does not directly subclass any particular kind of Morph, but rather she
assembles Morphs and gives them special state and behavior by associating them
with "Players", which are the fundamental user-scriptable object
types for User Scripting."
It is described in detail
(including a tutorial) by Squeak Central in "Programming in Morphic".